Titanium metal has been essential to the aerospace industry since the early fifties because it combines a high strength to weight ratio with the ability to perform at much higher temperatures than aluminum or magnesium. It also has growing usage in the chemical processing industries because of its excellent resistance to chloride corrosion. Recently the world demand for titanium has outstripped the limited production facilities causing it to be put on allocation in the United States.
Most of the United States primary titanium is imported from Japan and Europe. A majority of titanium is made by the "Kroll Process" which involves magnesium reduction of titanium tetrachloride, which is in turn made from rutile (TiO.sub.2). Titanium metal is also made by Na reduction and electrowinning. The product of the "Kroll Process" is a metallic sponge which is later consolidated by a high temperature arc melting process. The most important consideration for any process making titanium is to prevent contamination with either metallic or non-metallic impurities, because even small amounts of oxygen or nitrogen can make the product brittle and unworkable, although carefully controlled amounts of oxygen, nitrogen, and carbon may be added to strengthen titanium alloys.
U.S. Pat. No. 2,550,447 teaches a process for preparing titanium metal from titanium oxides ores such as rutile, anatase and ilmenite which comprises reduction of the ore by aluminum followed by iodination of the product obtained from such reduction. The iodinated product is then reacted with potassium iodide. Finally, titanium tetraiodide is removed from the potassium iodide and converted to titanium metal by either heat decomposition or reduction. This process is a very expensive method for making titanium metal.
U.S. Pat. No. 2,781,261 discloses a process for converting titanium dioxide to titanium by fluorinating titanium oxide, neutralizing the fluotitanic acid obtained, and reducing the neutralized fluotitanic acid with aluminum.
U.S. Pat. No. 2,837,426 teaches a process for converting ilmenite to an alkali metal fluotitanate by reacting ilmenite with sulfuric acid to form the titanium sulfate, removing a portion of the iron included with said titanium sulfate by reduction and precipitation of a reduced iron compound, and finally converting the titanic sulfate filtrate to an insoluble fluotitanate by means of an ammonium and/or alkali metal fluoride solution.
U.S. Pat. No. 2,857,264 teaches a process for preparing an alkali metal chlorotitanate by digesting ilmenite in a mixture of sulfuric and hydrochloric acid. Again, the iron present is precipitated out as ferrous sulfate and then further recovered by the addition of HCl to precipitate a ferrous chloride. Finally, potassium chloride is added to salt out potassium chlorotitanate which may be reduced with a Group I metal to titanium.
U.S. Pat. No. 3,012,878 teaches a process for reducing titanium halides to titanium metal by use of sodium metal.
U.S. Pat. No. 3,825,415 teaches a process, similar to the process disclosed in U.S. Pat. No. 3,012,878, except that the process is carried out in the vapor phase.
U.S. Pat. Nos. 4,127,409 and 4,072,506 are related to the recovery of zirconium and hafnium, respectively, by the reduction of the corresponding potassium chlorozirconates or hafniates by means of an alloy of aluminum and zinc.